Cameras with autofocus typically include an optical system consisting of a sensor, a control system, and a tunable optical element to automatically focus the camera on a selected point or area. Autofocus implementations can be categorized as being active, passive, or a combination of both (hybrid).
Passive autofocus systems typically used in digital single-lens reflex (DSLR) cameras can struggle to achieve accurate focus in low-light and low-contrast situations, while active autofocus systems typically used in fixed lens point and shoot cameras may be limited by a small number of focus points.